It is a long-standing objective of color photographic origination materials to maximize the overall response to light while maintaining the lowest possible granularity. Increased photographic sensitivity to light (commonly referred to as photographic speed) allows for improved images captured under low light conditions or improved details in the shadowed regions of the image. In general, the overall light sensitivity provided by the light sensitive silver halide emulsions in such systems is determined by the size of the emulsion grains. Larger emulsion grains capture more light. Upon development, the captured light is ultimately converted into dye deposits which constitute the reproduced image. However, the granularity exhibited by these dye deposits is directly proportional to the grain size of the silver halide emulsion. Thus, larger silver halide emulsion grains have higher sensitivity to light but also lead to higher granularity in the reproduced image. Therefore, it is a fundamental problem in photography to improve the light sensitivity of a silver halide element without a corresponding decrease in another property such as granularity. In this description, it will be understood that the demonstrated increase in sensitivity is accomplished without a significant sacrifice in granularity. Stated from another perspective, it has been a long-standing problem to provide materials which maximize the response to light of a silver halide emulsion for any given grain size.
For example, it is well known that highly reactive couplers or couplers that form dyes with high extinction coefficients can maximize the response of silver halide emulsions. However, the increased amplification caused by these types of dye forming materials also directly leads to higher granularity.
It is highly desirable to provide non-imaging materials that lead to increased photographic speed without having to increase the size of the light-sensitive silver halide grains.
Many different classes of heterocyclic materials are known to affect silver development in some manner and have been called, for example, antifoggants, fog restrainers, development restrainers, development inhibitors and stabilizers. Descriptions of these materials can be found in The Fundamentals of Photographic Technology, Silver Salt Photography, compiled by the Photographic Society of Japan (Corona, Ltd.), p 354; Chemistry of Photography, A. Sasai (Shashin Kogyo Shuppan Co, Ltd.), pp 168-169 and T. H. James, Ed, The Theory of the Photographic Process, 4.sup.th Edition, Macmillan Publishing Co, New York, Chapter 13, Section J. Commonly, these materials all contain an NH or SH group which allows them to bond or strongly adsorb to the silver surface and whose silver salts have a pK.sub.sp (-log K.sub.sp) of more than 10, where K.sub.sp is the solubility product in water at 25.degree. C. It is well known to add these materials to silver halide emulsions in conventional color photographic systems to limit or decrease their development. These materials are generally at least partially water soluble or soluble in water-miscible solvents such as methanol and are added directly to silver emulsions before coating of the film or added directly to the developer solutions. It is also known to attach these types of heterocycles covalently to PUGs (photographically useful groups) so that the PUG will be held in close proximity to the silver surface, for example, see U.S. Pat. No. 5,100,761.
U.S. Pat. Nos. 5,032,499, 4,837,141 and JP 62-138850 describe the use of a wide variety of photographic restrainers (including diazoles, triazoles, tetrazoles and tetraazaindenes) in thermally developable light sensitive materials. JP 10-50047 describes a wide variety of anti-silver sludging agents (including diazoles, triazoles, tetrazoles and tetraazaindenes) in a non-light sensitive cleaning film.
Substituted purines (1,3,4,6-tetraazaindenes) and other bicyclic heterocycles are known to be useful in photographic systems as antifoggants; for example, as in Japanese Patent Applications JP 07-281345A2; JP 03-013934A2; JP 03-138639A2; JP 04-107446A2; JP 04-067140A2; JP 05-127290A2; JP61-256346A2 and EP-741319A1 and as described in E. J. Birr, Stabilization of Photographic Silver Halide Emulsions, Focal Press, Ltd, 1974, pp 82-93. Purines are also described in Def. Publ. U.S. Pat. No. 877,011 to be useful as silver pi-complex stabilizers in photographic systems. Purines used as inhibitor fragments as part of a DIR ("Development Inhibitor Releasing" coupler) are disclosed in U.S. Pat. No. 3,933,500. Purines as a blocking group for the release of photographically useful groups during processing are described in JP 04-186344A2 and EP-335319A2. Derivatives of 6-aminopurines as addenda in high contrast black and white media have been described in JP 10-104784A2; JP 10-228077A2; JP 09-106024A2 and JP 04-336538A2. U.S. Pat. No. 5,411,929 and U.S. Pat. No. 5,328,799 describe the use of purines (including 6-dodecylaminopurine (inventive compound AA)) in thermally processed image recording materials. JP 02-62532 describes the use of purines in a layer adjacent to an imaging layer in a high contrast black and white graphic art film system.
Water soluble 1,2,3a,7-tetraazaindenes are known stabilizers and antifoggants; for example, see JP 07-281334A2; JP 06-347954A2; JP 06-230511A2; JP 05-127279A2; JP 05-232618A2; JP 03-241339A2; JP 62-055644A2; JP 60-173546A2; DE-2609993; DE-2419798 and E .J. Birr, loc cit. Water soluble 1,2,3a,7-tetraazaindenes are known to be useful addenda for silver halide precipitation as described in JP 61-014630A2; Czech Patent CS-255602 and U.S. Pat. No. 4,643,966. Water soluble thiol substituted 1,2,3a,7-tetraazaindenes are described as silver sludge preventers in JP 10-148917A2, EP 652470A1 and JP 08-137043A2 describes the use of tetraazaindene substituted hydrazines for use as development accelerators. JP 01-019343A2 describes the use of polymeric 1,2,3a,7 and 1,3,3a,7-mercaptotetraazaindenes.
Water soluble 1,3,3a,7-tetraazaindenes are well-known stabilizers and antifoggants; for example, see E. J. Birr, loc cit, and T. Tani, Photographic Sensitivity, Theory and Mechanisms, Oxford University Press, New York, 1995, Section 6.5. In particular, 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene (ClogP (as hereinafter defined)=-0.27) is widely used in photographic film. It is also known (for example, see T. Tani, loc cit, pp 191-194 and the references within) that this particular compound can cause increased photographic speed under some circumstances. Less water soluble 1,3,3a,7-tetraazaindenes with ClogP less than 6.0 have been described in JP 08-262601A2; EP 574331A2; JP 01-097946A2 and EP 197895A2. JP 06-059363A2 describes the use of polymeric 6-hydroxy-1,3,3a,7-tetraazaindenes as addenda for silver halide precipitations. Czech patent CS 255602B1 and Russian patents RU 2091846C1 and RU 2091858C1 describe the use of 2-heptyl-4-hydroxy-5-bromo-6-methyl-1,3,3a-tetraazaindene (ClogP=3.82) as an addendum for silver halide precipitations. JP 07-270955A2 and JP 07-270957A2 describe the combination of hydrazines with less water soluble tetraazaindenes with ClogP of less than 6.0. JP 10-221805, JP 09-265150A2; DE 3924571A1; EP 335319A2 and DE 2363308 all describe 1,3,3a,7-tetraazaindenes as suitable blocking groups for the release of photographically useful groups during processing. JP 52-154631 describes the use of certain 1,3,3a,7-tetraazaindenes as an inhibitor fragment as part of a DIR. DE 2053714 discloses the use of amides in combination with water soluble tetraazaindenes. JP 09-265150A2 discloses the use of 4-tribromomethylsulfonyl-6-pentadecyl-1,3,3a,7-tetraazaindene (ClogP=8.97) for use in thermally developable systems.
JP 05-333496A2 describes the combination of pyrroloazole cyan couplers with a wide variety of 1,2,3a,7- and 1,3,3a,7-tetraazaindene compounds in a color photographic print system using silver chloride emulsions for the purpose of improving cyan color in rapid processes. Out of 28 examples of tetraazaindenes shown, Xa-1 (ClogP=7.96), Xa-5 (ClogP=8.19), Xa-10 (ClogP=8.46), Xa-22 (ClogP=7.92), Xb-1 (ClogP=8.20) and Xb-4 (ClogP=8.74) have ClogP greater than 6.2.
JP 07-168303A2 describes a wide variety of 1,3,3a,7-tetraazaindenes in combination with hydrazines in high contrast graphic art materials using silver chloride emulsions for improved storage stability. Out of 48 examples of tetraazaindenes shown, only 2-(2,5-di-t-pentylphenoxy)-4-hydroxy-5-bromo-6-methyl-1,3,3a,7-tetraazaind ene (III-7; ClogP=7.73) has a ClogP greater than 6.2. JP 7-261308 describes a number of ballasted triazoles in a similar high contrast graphic art material.
U.S. Pat. No. 5,187,054 describes the use of ballasted heterocycles that contain a NH bond but do not contain any thiol substituents in a top layer to prevent silver sludging. Of the compounds shown, the highest ClogP of a benzimidazole (I-8) is 7.15 and a triazole (I-7) is 8.60.
JP 63-24255 describes a wide variety of diazoles, triazoles, mercaptotetrazoles and benzotriazoles, all with ClogP of less than 5.0, in a color photographic film. U.S. Pat. No. 4,770,991 also describes a wide variety of mercapto-1,2,4-triazoles (maximum ClogP=6.43), mercaptothiadiazoles (maximum ClogP=5.14) and mercaptotetrazoles (maximum ClogP=7.02) in a high contrast black and white film. JP 63-100446 describes the use of mercaptooxadiazoles (maximum ClogP=5.18) and mercaptothiadiazoles (maximum ClogP=4.12) in a black and white film. U.S. Pat. No. 5,006,467 discloses the use of 1,2,3-triazoles (maximum ClogP of examples shown=5.10) and EP 0 157 322 B1 discloses 1,2,4-triazoles (maximum ClogP=5.99) as antifoggants.
U.S. Pat. No. 4,528,264 describes the use of polymeric benzotriazoles prepared from benzotriazole monomers with ClogP of less than 5.0.
U.S. Pat. No. 5,508,154 describes the use of 5/5 bicyclic heterocycles in which one ring is a 1,2,3-triazole, and both rings together contain a minimum of 4 nitrogen atoms as antifoggants in systems that contain inhibitor releasing couplers. Of the examples shown, these heterocycles have an average ClogP of 1.53 with a maximum of 5.67 (example A-7). The patentee also notes that 6/5 membered bicyclic heterocycles with 4 nitrogen atoms do not produce the desired result.
U.S. Pat. No. 5,702,877 describes the use of ballasted benzimidazoles to improve granularity particularly with certain pyrazolone image couplers.
A problem to be solved is to provide color photographic elements that exhibit improved photographic speed and methods for processing such elements.